Abstract: The objective in studying and using polymer-based PTC (Positive Temperature Coefficient) materials is to increase PTC intensity of conductive composites and stabilize the reproducibility of the room temperature resistivity. On repeated heating cycling through the switch temperature or above it, the room temperature resistivity rises and the PTC intensity decreases. The effects of radiation cross-linking and continuous thermal aging in various atmospheres for a long time on the properties of the polymer-based PTC materials, such as the room temperature resistivity, PTC intensity, crystallinity and switch temperature, were studied. The results indicated that radiation cross-linking and nitrogen atmosphere were both favor of improving the electricity stability of PTC materials, the variety ratios of the room temperature resistivity and PTC intensity were relatively small.